class_docstr: A list-like structure to specify the order of items in a dictionary.
  The main characteristics are:
      - Append and insert only. Cannot remove elements. This is not strictly required
          by the use-case but probably good practice.
      - Elements must be unique. Inserting an element which is already in the list
          will throw an error.
  
  Primarily useful for specifying the order in which UI elements
  should be shown in Wave.
code: def __len__(self):
      return len(self._list)
  
file_path: h2o-llmstudio/llm_studio/src/order.py
imports: from typing import Iterable, List, Optional
label_desc: Use image node_id 7 for calling the Order obj's underlying member method code with example usage: obj.__len__() and returns: len